SPC AC 090551
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1251 AM CDT SAT APR 09 2011
VALID 091200Z - 101200Z
...THERE IS A MDT RISK OF SVR TSTMS FROM EXTREME SERN SD ACROSS SRN
MN AND NRN IA INTO SWRN WI...
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK FROM
CNTRL MN/WI...SWWD ACROSS SERN NEB INTO NWRN TX...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER OH VALLEY INTO
SC...
...SYNOPSIS...
A POTENTIALLY SIGNIFICANT WEATHER PATTERN IS DEVELOPING ACROSS
PORTIONS OF THE COUNTRY EAST OF THE ROCKIES OVER THE NEXT FEW DAYS.
OF PARTICULAR INTEREST SATURDAY WILL BE A CORRIDOR OF THE UPPER MS
VALLEY DURING THE LATE AFTERNOON INTO THE EVENING HOURS WHERE VERY
LARGE HAIL AND EVEN A FEW STRONG TORNADOES ARE POSSIBLE. ANOTHER
AREA OF ORGANIZED SEVERE IS POSSIBLE FROM PORTIONS OF THE LOWER OH
VALLEY...SEWD INTO SC.
...UPPER MS VALLEY...
UPPER RIDGING WILL GRADUALLY BREAK DOWN ACROSS THE UPPER MS VALLEY
DURING THE LATTER HALF OF THE PERIOD AS HEIGHT FALLS BEGIN TO
OVERSPREAD THE PLAINS IN RESPONSE TO A STRONG AND PROGRESSIVE UPPER
TROUGH OVER THE ROCKIES. PRIOR TO LARGE SCALE FORCING AFFECTING
THIS REGION...AN EARLY MORNING MCS OR REGION OF THUNDERSTORM
CLUSTERS WILL BE SHIFTING EAST ACROSS MO/IL. IN THE WAKE OF THIS
ACTIVITY...MOISTURE WILL SURGE NWD ACROSS ERN KS INTO ERN NEB/IA AS
LLJ BEGINS TO RESPOND AND INCREASE IN EXCESS OF 40KT DURING THE
AFTERNOON HOURS. AT THIS TIME IT APPEARS CAPPING WILL PREVENT
MEANINGFUL DAYTIME THUNDERSTORM DEVELOPMENT ACROSS THE MDT RISK
REGION AND BOUNDARY LAYER DESTABILIZATION SHOULD BE MAXIMIZED NEAR
THE MO RIVER ACROSS WRN IA BY 10/00Z. FORECAST SOUNDINGS ACROSS
THIS REGION SUGGEST INHIBITION WILL WEAKEN CONSIDERABLY WITHIN
CONFLUENT SFC FLOW AND THUNDERSTORMS SHOULD DEVELOP INITIALLY ACROSS
SERN SD/ERN NEB WHERE LOW LEVEL LAPSE RATES WILL BE MAXIMIZED. WITH
THE POTENTIAL FOR SBCAPE IN EXCESS OF 3000 J/KG VERTICAL SHEAR
PROFILES WILL PROVE VERY FAVORABLE FOR SUPERCELL STRUCTURES.
ADDITIONALLY...LOW LEVEL HODOGRAPHS STRONGLY SUGGEST THE POTENTIAL
FOR TORNADOES AS SFC-3KM HELICITY IS EXPECTED TO BE IN EXCESS OF 300
M2/S2. FOR THIS REASON A FEW STRONG TORNADOES COULD BE NOTED ACROSS
THE WARM SECTOR IMMEDIATELY SOUTH OF THE RETREATING WARM FRONT.
ONCE THUNDERSTORMS INITIATE ACROSS THIS REGION IT APPEARS AN UPWARD
EVOLVING AREA OF SEVERE THUNDERSTORMS SHOULD CONVERGE/EVOLVE IN AN
E-W FASHION ALONG THE WARM FRONT. WITH VERY STEEP LAPSE RATES AND
MUCAPE VALUES EXCEEDING 2000 J/KG ATOP THE COOLER AIRMASS SEVERE
ELEVATED SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL WILL EXIST
ACROSS SRN MN IN ADDITION TO THE LARGE HAIL THREAT WITH WARM SECTOR
SUPERCELLS.
ACTIVITY SHOULD ALSO DEVELOP SWWD DURING THE OVERNIGHT HOURS ALONG
THE ADVANCING SFC BOUNDARY ACROSS WRN IA INTO SERN NEB.
FARTHER SOUTH ALONG THE DRYLINE...STRONG BOUNDARY LAYER HEATING
ACROSS THE SRN PLAINS SHOULD EASILY REMOVE CONVECTIVE INHIBITION
ACROSS WRN OK INTO NWRN TX. SCATTERED THUNDERSTORMS ARE EXPECTED TO
DEVELOP ACROSS THIS REGION AS TEMPERATURES SOAR INTO THE 90S WHERE
SFC DEW POINTS HOLD IN THE UPPER 50S/LOWER-MID 60S. SHEAR PROFILES
WILL SUPPORT SUPERCELLS AND LARGE HAIL...ALTHOUGH AN ISOLATED
TORNADO CAN NOT BE RULED OUT NEAR DUSK AS LOW LEVEL WINDS BACK AND
BEFORE CONVECTION DECOUPLES FROM BOUNDARY LAYER.
...LOWER OH VALLEY SEWD TO SC...
AN EARLY MORNING MCS SHOULD BE ONGOING AT THE BEGINNING OF THE
PERIOD ACROSS PORTIONS OF MO/IL...AN EXTENSION OF ONGOING ACTIVITY
THAT IS EVOLVING/SPREADING ACROSS KS/MO REGION. LATEST MODEL
GUIDANCE SUGGEST STRONG BOUNDARY LAYER HEATING WILL DEVELOP AHEAD OF
THIS CONVECTION ACROSS KY INTO SRN WV AND AN UPWARD EVOLVING TSTM
THREAT WILL ENSUE BY 18Z WHERE NWLY MEAN SHEAR VECTORS ON THE ORDER
OF 50-60KT WILL ENHANCE ORGANIZATIONAL POTENTIAL. ALTHOUGH
SUPERCELLS WOULD SEEM POSSIBLE IN THIS ENVIRONMENT...IT/S POSSIBLE A
MORE ORGANIZED MCS WILL BE THE CONVECTIVE MODE AS EARLY MORNING
ACTIVITY SHOULD NOT COMPLETELY DIE OFF BEFORE BOUNDARY LAYER
DESTABILIZATION OCCURS. LARGE HAIL AND DAMAGING WINDS SEEM LIKELY
WITH THIS ACTIVITY.
..DARROW/HURLBUT.. 04/09/2011
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z